The present invention relates to a medical X-ray diagnosis apparatus and, more particularly, to an apparatus of the type using a television camera for converting an X-ray image to an electrical signal.
In the field of X-ray diagnosis apparatuses, apparatuses for digitizing an image signal and processing this digital signal have been developed. Particularly, in angiography, arithmetic operations for subtracting an image from another image are needed and it is necessary to store the image signals which are sequentially obtained from the TV camera into a memory and process them; therefore, digitization of the signals is effective for this image process. Such an apparatus uses a constitution such that the conventional X-ray television apparatus, namely, the apparatus for displaying the X-ray image of the object on the TV screen on a real time basis is combined with the digital image processing apparatus including an image memory.
In this real-time display mode (hereinafter, simply referred to as the fluoroscopic mode), it is necessary to use a low X-ray dose because the X-ray is continuously irradiated to the object. In this case, a long time lag characteristic is required for an image pickup tube to make up for a decrease in S/N ratio of image caused by high X-ray quantum noise .sigma..sub.q.
On one hand, to accumulate the image data into the image memory (hereinafter, simply referred to as the radiographic mode), the radiography of a high S/N ratio by use of a higher X-ray dose is desirable and a high time resolution or high spatial resolution is further required for the image pickup tube.
Moreover, in execution of the same radiography, a high resolution is required to observe, for example, fine blood vessels. On one hand, a high time resolution is required to observe the change in distribution of the contrast medium. As mentioned above, various characteristics are required for the X-ray television apparatus in dependence on a purpose of the observation and it is considered difficult to realize the apparatus which can satisfy wide application.